FIGS. 1 and 2 depict air-bearing surface (ABS) and side views, respectively, of a conventional perpendicular magnetic recording (PMR) head 10 used in recording a PMR media (not shown). The conventional PMR head 10 is typically used as a write head in a merged head including the conventional PMR head 10 and a read head. The conventional PMR head 10 includes a conventional first pole (P1) 12, P1 pad 13, insulator 14, a first coil 15, a second pole (P2) 16, a conventional PMR pole (main pole) 18, insulator 20, write gap 22, a shield pad 24, a second coil 26, and shield 28. The conventional PMR pole 18 has a height, h, and sidewalls that form an angle, θ, with the insulating layer 14. Although not explicitly shown, seed layer(s) may be used in providing the conventional PMR pole 18. In such a case, the conventional PMR pole 18 would reside on the seed layer. Although depicted as a single shield 28, it is typically composed of two portions 28A and 28B that are formed separately. The PMR head 10 is also depicted with two coils 15 and 26. However, PMR heads having a single coil may also be used.
In order to write data to a PMR media, the coils 15 and 26 are energized. Consequently, the PMR pole 18 is magnetized and the media written by flux from the pole tip 18A. Based on the direction of current through the coils 16 and 28, the direction of magnetic flux through the PMR pole 18 changes. Thus, bits having opposing magnetization can be written and the desired data stored on the PMR media. When the conventional PMR head 10 is not writing, no current is driven through the coils 15 and 26.
The conventional PMR pole 18 may be plated or may be sputtered. A plated PMR pole 18 may suffer from a reduced magnetic moment. In addition, one of ordinary skill in the art will recognize that domain lockup, also termed remanent erasure, is an issue for plated PMR pole 18. Domain lockup occurs when the conventional PMR head 10 inadvertently erases data in the PMR media even though no current energizes the PMR head 10. This occurs due to a remanent field (a field/magnetization when there is zero current through the coils 15 and 26) remaining the PMR pole 18. Stated differently, the PMR pole 18 may not completely demagnetize when in a quiescent (zero current) state. Further, the pole tip 18A is sufficiently small that such deviations of the magnetization domains in the PMR pole 18 from a completely demagnetized state may produce significant magnetization in the pole tip 18A. As a result, a high remanent field may be present in the PMR media even when no current is driven through the coils 15 and 26. This remanent field may erase data recorded on the PMR media after the head 10 passes over the media for many revolutions. Because it involves this inadvertent erasure, domain lockup is undesirable.
Domain lockup may result not only in inadvertent erasure of data, but also failure of the PMR media. The servo areas (not shown) of the PMR media are usually written at much lower linear density than the areas that store user data. Consequently, the servo areas are more subject to being erased by the remanent field of the PMR head 10. Erasure of servo areas may cause complete drive failure. Therefore, it would be highly desirable for domain lockup to be eliminated.
Sputtered conventional PMR poles 18 may provide some relief from the issues of plated PMR poles 18. Sputtered, antiferromagnetically coupled magnetic layers may be used for the conventional PMR pole 18 in an attempt to reduce domain lockup. Because of the antiferromagnetic coupling, when in a quiescent state, the remanence magnetization of such a conventional PMR pole 18 is expected to be approximately zero. A zero remanence magnetization may be achieved along the hard axis of the PMR pole 18 using antiferromagnetic materials. However, in practice, a zero remanence magnetization may be difficult to achieve along the easy axis. Furthermore, the geometry around the pole tip 18A is complex. As a result, the easy and hard axes may be switched if the combination of shape anisotropy and magnetoelastic anisotropy along the pole tip 18A is larger than the induced anisotropy. Consequently, domain lockup may still be an issue for conventional PMR heads using sputtered antiferromagnetically coupled magnetic layers for the conventional PMR pole 18.
Accordingly, what is needed is a system and method for providing a PMR head having reduced domain lockup.